MIT prep for UK student

While I think it is okay to have dreams, I do not think this is attainable unless you are from a wealthy background. Both MIT and Harvard are situated in very expensive areas. Take into account living costs are up, you would be looking at around ~$30k just to live and survive in the general area per year. Next is the actual academic cost, while it may be brought down with scholarships, the base fee is ~$30k per term as per the MIT website - Harvard has on their site a cost of $82k per academic year (though this includes health insurance, housing, etc).
So ask yourself - are you (your parents) in a position to pay somewhere between $60000 - $90000 upfront per academic year? I doubt you will get US backed loans for this...
As per what you can do extracurricular wise, take a gander at one of these MIT portfolio videos

As a UK student in year 10 at a vocational high school(UTC) I study engineering and want to study this in MIT or Harvard but what extracurricular activities can I do such research programs,STEM challenges or clubs??Also, I do not have a lot of knowledge on subjects outside of the curriculum what resources can I use to study more / prepare for A Levels / study for challenges.

Both MIT and Harvard and need-bind and full need for all students including international, so means-tested funding should not be a concern. The acceptance rate for both these schools is a different matter - they accept less than 4% of applicants overall, and it is below 1% for international students as they limit their international intake to no more than 10% of all available places each year. Literally, they accept only maybe 1-2 students from the UK each year, so the applicants have to be exceptionally excellent, and these schools cannot be the only options to apply to, since they have a 99% chance of rejection.

You are right to start preparing for the application early - good planning!
Firstly, you should look at which exams you will be taking at your current school. US universities are very familiar with A-levels and GCSEs - but not with BTECs or any vocational qualifications. So it may be difficult to get them even accept non-standard or less academically demanding qualifications, and you have to plan your studies accordingly.
Also, check their current subject requirements - they usually expect you to complete a standard high school curriculum in the last 4 years of your school, such as 4 years of English (it is OK to take 2 GCSEs - English and English Literature - 2 years each, simultaneously), 2 years of each of full sciences, a foreign language, a social science etc. If you narrow your studies down too early, you will already not meet their entry requirements.
Besides, these schools have HASS (Humanities, Arts, Social Sciences) requirements to complete a wide range of courses within their programmes, so if you do not enjoy English and humanities, and really want to focus on engineering only, you will struggle in their programmes and may be better off applying to a purely engineering school, not to a liberal arts college like Harvard.
Obviously, you have to have very strong grades in all your exams - they convert them to GPA, and every grade counts towards it. Most strong applicants have near-perfect GPA.
You also need to start preparing for SAT/ACT test - tests are now mandatory for both schools, and the average score of admitted MIT applicants is near-perfect range - like for SAT, 99% of admitted applicant have the score of 790-800 in Maths and 750-800 in English. Test scores form a part of your academic profile for the admissions purposes.
Finally, in terms of extracurriculars etc, since you are in an engineering college, you should look to complete some interesting projects building things - could be physical or software products. Look up MIT maker portfolios videos on YouTube to get an idea what people do. Just note that you cannot include any of your schoolwork in extracurricular activities - they really want you to do these things in your own time. You can also look doing some research projects if this interests you.
Also, find some volunteering activities linked to engineering or some of your other passions, so you have a few activities to show for each passion to show depth, and these schools really want you to try and make the world around you better.
I responded to another comment here, that the financial side should not be a concern since both these schools are need-blind and full need for international students (if they offer you a place of course!).
Finally, look at Sutton Trust programme and apply if you qualify - they offer full support with US universities applications. Also, Fulbright has a lot of information and runs regular events covering US unis admissions.

Thank you. Unfortunately I do not study humanities ,social science or a foreign language currently but would I still be able to apply?
I study English literature, English language, Engineering(vocational), IT(vocational), physics, bio, chem, maths and computer science.
In addition I previously studied French for 8 years(in primary school aswell as high-school 2 years), German for 3 years, geography 3 years, history 3 years, RE for three years , drama for one year, graphic communication for 1 year and art for 2 years. Would they be able to take this into account?
For a-levels I plan to study maths, physics, further math and economics(counts as an HASS subject) and I will study to take an ACT test towards the middle of year 12.

It is best to email MIT Admissions and ask if your subjects satisfy their recommended school curriculum, and what you can do to improve it. US unis' Admissions are like marketing departments - lots of staff and high budgets- they are available all year round and are happy to provide all info you need - your questions will show your interest and initiative, so there is no downside to asking.
Economics is a social science by the way, so that requirement is covered.

As a UK student in year 10 at a vocational high school(UTC) I study engineering and want to study this in MIT or Harvard but what extracurricular activities can I do such research programs,STEM challenges or clubs??Also, I do not have a lot of knowledge on subjects outside of the curriculum what resources can I use to study more / prepare for A Levels / study for challenges.

THANK YOU so much I was quite worried and unsure due to the requirements I will do that for sure!

like the previous comments said, its extremely difficult to get into topUS schools like Harvrad or MIT. if ur not rich and dont go to eton, i would highly suggest looking at programs/sixth forms that match ur dreams. Off the top of my head, NCS would probs be a good sixth form for u since they are the top state skl in UK which sends students to Harvard and MIT each year. i rmb seeing them on national news aswl but defo check out their website and apply if u live in London. Another great program is Sutton Trust US program but previous comments already mentioned this. If possible, i would say do both as it would maximise ur chances at getting into MIT or harvrad. With US unis, its unchartered territory so having alumni connections like NCS does, like Sutton Trust does, means that u can speak with previous students who got into those skls +more and get advice directly from them. Barely anyone in the UK gets into these skls so having the chance to speak to those few is INCREDIBLY advantageous

That's great because I was planning to apply to study at NCS for sixth form however i am worried as to whether or not I would accepted

this will probs sound quite harsh and im sorry but if u cant even get into NCS, then i doubt u can get into harvard or MIT. The grades required for Harvard/MIT is much higher and more difficult and to be quite frank, u need to be securing majority 9s regardless. however since ur in y10 u have more than enough time. js use mygcsescience.com for science, use mathscloud aiming for grade 7 and aming for grade 9 question packs, do ur daily corbett 5 a day foundation +, higher and higher + questions and u should easily get 9s. do past papers from 2015 onwards starting now and u should be easily get 9s

I would copy the extracurricular activities, research programs, STEM challenges, and club positions of people admitted to MIT and Harvard. A student might choose a major on the application, then change majors after they start university. Harvard students wrote their personal essays about learning resilience by overcoming a challenge or negotiating with someone, for example one's parents, to get what s/he wants. It seems that Harvard values these topics. I am not sure. I think Harvard values letters of recommendations from high status people, such as partners of prestigious firms, celebrities, government officials, or politicians. Harvard accepts people from feeder schools.
Someone from England applied to MIT and was rejected. She had high grades, but little to no extracurricular activities. It seems that MIT values extracurricular activities along with grades.
To prepare for A-levels, I would read the top band of the mark scheme and do what is needed for top marks, for example doing past papers with a timer.
I don't know if you would benefit from the memory technique spaced repetition during the years of A-levels.
To prepare for STEM challenges, I'd look at the questions and solutions.